Lithium-ion batteries normally operate 3.7V per cell — but Kentli put circuitry inside the cells to reduce the voltage to 1.5 volts. The company claims that the batteries have a capacity of 2800mWh which matches Eneloop Pro (the NiMH batteries with the highest capacity).

Additionally, Kentli batteries are lighter than Eneloop Pro. However, they are more expensive. A four pack of Eneloop Pros costs about $17, whereas a 4 pack of Kentli cells costs about $34.

Other Lithium-Ion Rechargeables

There are also some lithium-ion rechargeable batteries made for high-performance flashlights and cameras, in these sizes: 18650 and CR123.

A single 18650 battery can replace two CR123A batteries, although at a lower voltage (but much higher amperage). However, the 18650 is a wider cell and will not fit into a flashlight that is designed strictly for the narrower CR123As. Most modern tactical LED lights are designed to use a single 18650 or two CR123As, but it’s best to check before buying. See our article on The Best 18650 Batteries for more information.

There are also numerous other types of lithium-ion batteries made for specific laptops and other electronics gadgets. There is currently no standard size for these lithium-ion cells.

Comments 31

It would appear that NIMH rechargeable cells are better than these for most applications, given their higher capacity and lower cost. The most important difference is that these cells output 1.5 volts, like conventional AA cells, while nickel-metal-hydride cells provide only 1.2 volts. If you have a device that doesn’t perform well with the lower 1.2 volt supply, then this rechargeable Lithium-Ion AA technology may be a welcome replacement for disposable conventional 1.5 volt cells.

There is a 14500 rechargeable Li-ion cell that matches the physical dimensions of a AA cell, but it outputs 3.7 volts which may be too high for some devices. Some small flashlights are designed to use AA cells at 1.2-volts (NIMH) to 3.7-volts (14500 Li-ion).

This article states that a single 18650 battery can replace two CR123A batteries, but that is not exactly correct. The 18650 has a larger diameter than the CR123A, but the article fails to point out that you can get a 16650 rechargeable Li-ion battery that will fit the same enclosure as two (disposable) CR123A batteries stacked end-to-end. An important issue is the difference in output voltage. Two CR123A batteries in series will supply a total of 6 volts, while a single 16650 (or an 18650) will supply only 3.7 volts. In some flashlights, for example, the light output will be brighter with the 6-volt supply of the two CR123A cells. The downside is that you will be throwing away $3 to $4 worth of disposable batteries each time they run down.

Other folks have pointed out the incorrect claim that this cells capacity of 2800mWh matches the Eneloop Pro, which lists a capacity of up to 2550mAh. What many shoppers don’t realize is that “mWh” (milliwatt hours) and “mAh” (milliamp hours) are not measuring the same thing. 1000 milliwatt-hours, at 1.5-volts, equals only about 667 milliamp-hours. Since almost all battery sellers state battery capacity in “mAh”, milliamp-hours, one might question the integrity of a seller that uses a different unit measurement to make their battery capacity sound better.

These batteries are deceptively labeled by the manufacturer, who has listed the capacity in mWh rather than mAh. When you convert 2770mWh into mAh for a 1.5V output, you get a much less impressive figure of 1847mAh, which is significantly lower than the Eneloop Pro’s rating of 2500mAh. I honestly don’t see the point of these, unless you have some edge case requiring AA form factor AND rechargeable cells BUT lower weight than NiMH, AND unable to use NiCd (which are FAR lighter – competitive with traditional consumable lithium).

Not so fast. Not sure what protection is built-in to these cells, but it better be pretty dang robust. Without proper protection circuitry, if you(or your kids…) accidentally throw these in the charger you use for your NiMH AAs they will explode violently. Also, there is probably step-down circuitry in the cells that convert them to the nominal 1.5v. This circuitry will likely incur some losses which usually mean additional heat is generated, which likely also means that the max output amperage is limited as well. The charging procedure for Lithium cells is much different and much more unforgiving than NiMH. So, to pack that ciruitry into the cells means less storage media inside and thus less capacity. Quality NiMH cell already provide much more run time than one time use cells. And more than these as well. The cost benefit just isn’t worth the risk IMHO. Of course these brands that I’ve never heard of may be on the cutting edge of technology and have already solved these issues, but I’m not betting on it. My bs detector is maxed out on these. Feel free to correct me if I’m wrong.

Pretty sure you missed the point of these “new” cells. They are AA sized cells with 1.5V output. They are not like 18650’s that output 3.7V. They contain circuitry to reduce voltage to 1.5, and hopefully disallow charging in normal NiCad and NIMH AA chargers.

As an update there are several brands of Li-ion rechargeable batteries on Amazon now. And some of them are advertising 3200mWh or 2133mAh. Sadly I would have to buy a new charger as well, and I am not planning on abandoning my $50 charger and my Powerex 2700mAh batteries without some new breakthrough in Li-ion or Li-Po batteries.

While Li-ion generally packs more energy in the same space as other battery technologies there are reasons why it doesn’t do well in AA/AAA applications. Li-ion cell voltage runs normally at around 3.7 V where all alkaline based batteries (what AA is built around) run at 1.5 volts. In addition Li-ion is inherently dangerous without circuitry to protect it. As such, making a AA sized li-ion battery requires sacrificing space in the battery for electronics to change the voltage and keep the battery safe. This reduction in space for electrochemical storage is why they do not really outperform Ni-MH right now. When you get to bigger sizes that can run at their nominal 3.7 volts, like an 18650, the improvement over other battery types is significant. As an example, trying to replace the cells in a laptop with the equivalent in NiMH would not come close to fitting in the same space.
Due to the safety of Li-ion and the fact that these batteries have not undergone strict US testing/manufacturing standards it is recommended to stay with rechargeable NiMH in the time being. Hopefully, one day, Li-ion will improve enough that a AA type battery will exist that offers major improvement over NiMH. Right now their is little benefit (slightly better power, faster charge, and number of charge cycles) to outweigh the risks with li-ion cells of unknown quality. If it was that good you’d see the major US battery companies selling it, and they don’t so a good indicator something is off.

There’s what you might call the “native voltage” of the chemistry of a battery, called the nominal voltage. For NiMH batteries, this is 1.2V. For alkaline cells, it’s 1.5V. For the type of lithium ion chemistry used in those batteries, the nominal voltage is 3.7V. So, you throw the chemicals in a jar with your 2 electrodes, and that’s the voltage you’ll get. You can’t get lower. Hence the need for the circuitry to bring it down to 1.5V

I am loving the tenavolts, i have also tried the altizure which are 1.9v (could damage things) but have very low capacity, and I am going to try out deleepow next. The tenevolts power underccabinet lightning and run them for 7 days at a time (5-8 hours each day of use). Each light uses three tenevolts.

good catch, a bit of trickery there. However tenavolts webpage indicates only 750mAh. I don’t understand the disparity. Your calculation, dividing Wah/V should be correct.
Amp hours (mAh) X voltage = mWh
volts = Amps * Resistance. Watts = Amps * Amps * resistance. m = milli, a prefix to indicate the small amount (without the m 2800mA = 2.8A)
I assume this involves the conversion from ~3.7 volts to 1.5. 750 X 3.7=2775, but power is 1.5 X amps permitted through converter. So 2800mWH/750mAh=3.7
I would assume there was some Voltage conversion loss as well. There are some things about these numbers that are a bit concerning….

I feel I must echo what only one person has correctly pointed out in response so far (but for some reason has not been up voted as due for his correctness), for those of you who are not completely “in the know” – There indeed ARE Li-ion batteries that are the same form factor (size/shape) as traditional AA and AAA batteries.
They are increasingly popular for high-drain devices such as high output LED flashlights (of which I have a few), and they are often THE cells that are being mentioned in things like laptop batteries and wireless rechargable hand tools.
Crack open a 6-cell laptop battery and you’ll be likely to find six of the very same Li-Ion AA sized cells you can buy on eBay/Amazon shipped from China.
They are often welded together in groupings that increase the total voltage to that needed by the 12 volt laptop requires.

I purchased two solar powered garden lights. they have AA 3.7V 600 mAh Li-ion batteries with a 14500 number. Do you know if there is a replacement battery for these, since they are very difficult to find? I am about to give up on finding any.

I’m surprised nobody has done a double-AA L-iIon or Li-Po battery – same form factor as two AAs next to each other without the extra voltage circuitry (assuming things can handle a bit extra voltage). Depending on how the “connection” is done, there could be room for quite a bit of extra power.